||In Germany data protection is very dominant. The German property market is, as in other countries, not standardized. So the question how to get reliable information as a foreigner is even more important. Especially data protection has not prevented the availability of market data, but as a consequence of the analysis of each purchase contract, by the public experts committees, many qualified indirect comparative data have been published which can be used. In the lecture the published data, as the market reports of the experts committees the market data published by the estate agents associations and other private institutions are presented. It is shown how to use the indirect comparative data in a way corresponding to the market. Apart from this the separate institutions, who publish market data, are presented with contact partners. Indirect comparative data are derived from market data and demonstrated by practical examples. A critical answer is given to the question if the data protection prevents transparency of the market or if it even is able to support it.